1. Field of the Invention
The present invention relates generally to an exhaust gas recirculation control system used for a diesel engine, and more specifically to an exhaust gas recirculation control system controlling the throttle valve in addition to the control of the exhaust gas recirculation valve such that exhaust gas recirculation can be optimized in accordance with the engine operating conditions including engine load.
2. Description of the Prior Art
As in an gasoline engine in general, a diesel engine is provided with an exhaust gas recirculation system, whereby an inert exhaust gas is recirculated within the combustion chamber in order to lower the combustion temperature, that is, to suppress the generation of NO.sub.x contained in the exhaust gas as an injurious component.
In the prior-art exhaust gas recirculation control system, however, since the control lever of the fuel injection pump and the throttle valve are both linked with the accelerator pedal mechanically, the force required to depress the accelerator pedal increases and the exhaust gas recirculation control valve opens a little to perform the recirculation operation even when the engine speed is low under a relatively heavy load. In addition, the intake air loss due to improper throttle valve operation causes incomplete combustion, resulting in emission of a large amount of smoke.
A more detailed description of the prior-art exhaust gas recirculation system will be made hereinafter with reference to the attached drawing under DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS.